At the bottom of the earth sits a massive bowl of ice that you may know as the West Antarctic Ice Sheet. Every day the sea washes away from its base, slowly eroding the glaciers that line its edge. When they inevitably give in, the sea will begin to fill the basin, claiming the ice for itself and flooding coastlines around the world.
Thwaites Glacier is one of the redoubts that guard against the collapse of this critical ice sheetmost of which rest below sea level and contain enough ice to lift the sea 60 meters. Unfortunately, this icy goliath, the size of Florida, is also one of the world’s most unstable and fastest melting glaciers. While glaciologists knew that the rate of ice loss was severe, they recently discovered that it was exposed to much more warm water than previously believed. In a study published this week scientists using satellite imagery and hydraulic modeling found that warming tidal currents penetrate the massive block of ice at depths as great as 3.7 miles, causing “strong melting.”
“We really, really need to understand how fast the ice is changing,” said Christine Dow, an associate professor of glaciology at the University of Waterloo and one of the study’s authors. “We were hoping it would take a hundred, 500 years to lose that ice.” Although the researchers do not know how much faster the ice is melting, they are concerned that within a few decades.
As climate change drives global temperatures ever higher, glaciers and ice sheets in polar and mountainous regions are inevitably melting. The water and disrupted ice flow into the oceans, causing them to rise. Since 1880, global sea levels have risen about 9 inchesand any sudden increase can be catastrophic for coastal cities such as New York, Mumbai and Shanghai. Low lying countries like the Marshall Islands and Tuvalu can be completely submerged.
Thwaites Glacier, often dubbed the “doomsday glacier,” already responsible for 4 percent of the planet’s sea level rises and falls 50 billion tons of ice annual. When it collapses, it can raise oceans worldwide 65 centimeters, or just over 2 feet. “It doesn’t sound like a lot, but when you think about how much seawater we have in the world, it’s a huge volume,” Dow said.
The study, published in Proceedings of the National Academy of Sciences, found that the pulsation of tides, which raise and lower the ice, allows water to creep further under its shelf and its anchor to the seabed weakens. While the same team captures this phenomenon at Petermann Glacier Greenland, it was not recorded in Antarctica. Thwaites has about eight times as much ice in contact with the sea as Petermann.
Using high-resolution satellite imagery and hydrological data, the study identified high-pressure pockets where the glacier’s surface had been lifted, showing warm water flowing beneath the ice. Previous models used only the part of the glacier that touches the ocean as the “baseline” from which to calculate the potential speed of ice loss due to contact with warm, salty water. Now the paper says it may have found the missing link in modeling how glaciers change.
“This boundary is a very important aspect in geology regarding the glaciers’ response to a changing climate,” said Bernd Scheuchl, an Earth system researcher at the University of California-Irvine and co-author of the paper. He says a better understanding of how seawater can penetrate the base of a glacier could help scientists better predict ice loss across the West Antarctic Ice Sheet. “The whole region is the gateway to an area that is far below sea level.”
Predicting the speed of ice loss and sea level rise is no easy task. Ever-shifting factors, such as the amount of greenhouse gas emissions, can slow or accelerate global warming, and in turn the rate at which glaciers melt. And modeling glaciers, which are hydrologically dynamic, remote and difficult to research, is a technological challenge that computers have only recently been able to handle, according to Dow.
Sharon Gray, a marine scientist at the nonprofit Rising Seas Institute, says research breakthroughs like this help the world prepare for and adapt to disappearing coastlines. “It’s never going to be perfect,” she said. “But of course, the better we can get our models, the better we get our projections that help us plan.”
Given the complexity and uncertainty of modeling, Gray said it’s best to assume seas will rise to the highest forecast level and prepare for worst-case scenarios. Some high-risk places, such as Singapore and the The Netherlands, is doing just that and has invested in infrastructure to meet the challenge. “I think there’s hope and an opportunity to really think creatively and try to wrap our heads around what’s coming and what we can do about it,” she said.
Researchers like Dow and Scheuchl say the best way to protect glaciers is to limit carbon emissions. Although the heat that humanity has already put into the atmosphere will continue for centuries and glaciers will continue to melt, limiting the amount the planet warms could buy time to prepare for, if not prevent, the most extreme outcomes.
“It’s never too late to make a change,” says Scheuchl. “Even if we cannot stop these developments, we can slow things down and reduce their impact.”
